1. Field of the Invention
The present invention concerns the domain of engine compressors, particularly of aircraft jet engine compressors incorporating air bleed systems.
2. Description of the Related Art
It is known that the compression system of a jet engine (and in particular, the high pressure compressor) is one of the most critical components of the engine. The compressor of a jet engine is made up of several successive compression stages, each stage comprising a moving cascade of vanes (rotor) and a fixed cascade of vanes (stator).
As it passes into a fixed cascade of vanes, the air is diverted, causing a loss of speed and an increase in pressure. In these conditions, aerodynamic losses due to friction, also called diffusion losses, occur. These losses result in a degradation of compressor performance. In the vicinity of the walls of the airflow channel, these losses combine with friction losses along the walls and form 3D flows causing additional high losses.
Furthermore, it is known that, in the case of an aircraft jet engine, air at high pressure is generally bled off inside the high pressure compressor, principally for cooling requirements or for operating various systems of the jet engine or aircraft.
An installation with cascades of vanes is known from Patent FR-2 166 494, incorporating at least one cascade of vanes, fixed or moving, with a fluid flow passing through it, and comprising a succession of vanes supported by at least one side wall. Each passage defined by two successive vanes and the side wall incorporates at least one localized suction opening formed in this side wall and connected to suction means disposed such that the pressure at the suction openings is of the same order of magnitude as the static pressure of the local flow in the passage under consideration. Patent FR-2 166 494 furthermore provides a perforated wall arranged in a suction opening having an elongated shape, formed facing a passage between two successive fixed vanes, in a wall of the compressor casing, which serves to limit the suction rate.
On account of a large passage cross section enabling sufficient suction to be obtained, such a suction opening generally has dimensions which are large compared with those of the channel between two vanes. Therefore, as the pressure gradients in this channel are high, local fluid recirculation or ejection occurs. This recirculation, which interferes with suction, interferes with the airflow and reduces the efficiency of the air bleed system. This air bleed system is therefore not optimum, nor is the corresponding engine.
Furthermore, a compressor is known from document GB 2 407 142 that bleeds air at the passages between two vanes through openings made in a wall, which are discontinuous.